Refining of mineral oils



July 20, 1943. Q READ 2,324,952

REFINING OF MINERAL OILS Filed Feb. 10. 1940 .3 4 VENT .SEPA RA 7-COOLER .5534 RA'TOR L RA FF/NA r:

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' spective constituents is secured by suitable dis- Patented July 20,1943 UNITE D STATES f PATENT asrmmo or MINERAL OILS i.

Chester L. Read, W'estfield, N. J., assignor to Standard Oil DevelopmentCompany, a corporation of Delaware Application February 10, 1940, SerialNo. 318,249

2 Claims. (01. 196-13) The present invention relates to the refining ofmineral oils. The inventionis more particularly concerned with thesegregation of petroleum oils into their relatively more paraiiinic andinto theirrelatively more. aromatic constituents by means of selectivesolvents. In accordance with the process of the present invention,distinct improvements are secured in solvent treating operations bypretreating the feed oil in the presence of arelatively small amount ofthe selective solvent in a manner adapted to remove relatively minutequantities of substances which are entirely insoluble in the selectivesolvent under the conditions of operation and which would otherwiseresult inoperating difficulties. V

It is well known in the art torefine mineraloils and to segregate theseoils into their relatively more aromatic and into their relatively moreparaffinic constituents by means of various selective solvents. Inprocesses of this character the general procedure is. to-extract themineral oil with solvents of the class which have a preferentialselectivity for the relatively more aromatic type compounds as comparedto the relatively more paraffinic type compounds. Sol- Vents of thischaracter are, for example, furfural, phenol, sulfur dioxide, cresol,nitro benzene, aniline, beta beta dichlor diethyl ether, and the like;

7 The oil and solvent or solvent mixture are mixed in various types ofoperations undertemperatureand pressure conditions adapted to form ahighly aromatic or solvent extract phase and ahighly paraflinic orraflinate' phase. Although single or multi-stage treatments areemployed, the preferred process is a countercurrent tower treatingoperation, since it is continuous and permits a more economicaloperation. In a countercurrent tower treating process the lighter phase,usually the oil, is introduced at the bottom or at the center section ofthe tower. This phase flows upwardly through the tower and intimatelycontacts the downflowing heavier phase, usually the solvent, which isintroduced at or near the Complete mixing of the re tributing andcontacting means, such as distributing plates, pierced plates, contactmasses, and the like. If the oil is the heavier phase, the conditionsare reversed and the oil is introduced at the top of the tower, whilethe solvent is introduced at a lower section of the tower. In acountercurrent treating tower operation either the oil or the solventmay be the continuous phase, although it is generally preferred that thesolvent be maintained as the continuous phase. The efficiency of a'countercurrent treating tower operation is a function to a large extentof the e'fiiciency of the contact betwe'en the respective phases, aswell as upon thetime of contact. However, when usingcertain solvents,particu larly phenols, it has been found that-certain oils containconstituents which cause extended emulsification, of the, solvent andoil. This greatly lowers the overall efiiciency of the sol venttreating'operation, since the emulsification zones in effect decreasethe efiective area of the tower, resulting in a. decrease in capacity.and yields. My process, which comprises a pretreatment of theoil in thepresence of 'a relatively small amount of the Iselective'solvent,entirely eliminates emulsification and related operating, dimculties and.resultslin' unexpected improvement in tower capacities and in productsof improved quality. V,- fl

The process of my invention may bereadily understoodby reference totheattached drawing illustrating one modification ofthe same. Feed oil,which for the purposes of description is taken to be astocksubstantially free of asphalts and resins and boiling in the-petroleumlubricating oil range is introduced into the solvent treating system bymeans of line l ,The feed oil-is mixed with a relatively small amount ofsolvent, which for the purposes of illustration is assumed :to be aphenol, which is introduced into line I by means of line 2. Themixture'is passed through ature, and introduced into mainsolventtreating unit 8, which for thepurposes of description is assumedto be a countercurrent treating tower. The feed oil flows upwardlythrough tower 8 and countercurrently contacts substan tially the entirequantity of phenol which is introduced into countercurrent treating.tower 8 by I means of line 9. Efficient con-tact between the.countercurrently flowing phases is secured by adequate contacting meanssuch as distributing plates, contacting masses, pierced plates, and

the like. The selectivity and solvent power of the selective solvent maybe adjusted to any desired degree by the instroduction of a solventmodifying agent such as water into tower 8 by means of lines In, H, l2,and I3. Temperature and pressure conditions are adapted to secure theformation of a highly paraflinic or rafllnate phase which is withdrawnfrom tower 8 by means-airline M. .This phasemay be cooled in cooler .5or mixed .with a solvent modifying agent which is introduced by means ofline IS in order to secure a further phase separationiin separator IT.The precipitated solvent .rich phase is withdrawn from separator'l'lby'means of line I8 and handled in any manner desirable. This phasemay be returned to .theacountercurrent treating tower or utilized as anintermediate stream. Under certain conditions it maybe desirable to usethis phase relatively rich in 501- vent to dilute the feed oil prior topretreating'the same. The .relatively solvent poor phaseis withdrawn 1mm-separator n by means .of "line :19 and passed'to "solventiseparatorfllnwhich the solvent is "removed by -.means offline 21 and :returned 10solvent storage 12. A solvent-tree 'ramnate oil "is withdrawn by meansof line T23 and removed from the system.

"The solvent extract :phase may be similarly handled. This phase is"withdrawn Tfrom tower 18 by :means of '24 and 'may be cooled 'ineoiolerzi in order "to secure a. Turtlrer phase sep- 'aration inseparator 26. fPhase senaratton may be aided or entirely secured .by'theaddition of a solvent modifying agent which is fintroduced byxrreansof line -fl. The preclpitatedphase'is withdrawn 'tromseparatorlfi bymeans of fline -28. "and handled in any manner desirable. "This phasemay be returned ito the 'countercurrent -treating system .or removed -anintermediate product. The solvent "rich phase .is withdrawn fromseparator Zliby means of linen'and passed to solvent "recoveryunit 301mmwhich the solvent is removed "by means of line 3| andireturnedtosdlvertt storage 22. A' solvent-treeiex- 'tractiiswvithdrawntromunltmby means of line 32, removed from the system, :and .handled inanymanner desirable. Under pertain conditions 'be'desirahle to utilize asmall amount of relatively solvent rich phase withdrawn spective phases.These di'lhculties are generally measuredin terms or 'emulsrftcation. Ingeneral, I have found that these constituents comprise -lessthan about2% more feed oil and are gen- 'erally'in the *range from i01% to 115% ofthe reed'oil.

lhe amount of solvent introduced in the chargeo'il before pretreathigthe same .rn ay vary widely. The quantity-will upon the particularsolvent beingused *andthe character of the*ieed'oilbeingsolventtreatedgaswell as upon the temperature or the oil.it is "flesired to introduce sufficient solvent into the charge oil toapproximately saturate the oil with solvent which results in theprecipitation of substantially all of the solvent insoluble oil constit-5 uents without the formation of two phases containing an appreciableamount of the selective solvent. For example, when using henol, I havefound that it is desirable to dilute the oil with from about "6% to 20%0f phenol, ;preferably 10 from 10% to 112% of .phenol before.pretreating the same. This results in the precipitation of .about 0.01%to 0.5% of solvent insoluble constituents. The temperature of thepretreatment *maylikewise vary considerably, In general, thertemperature is preferably in the range below about '150-F.-dependingupon the particular solvent employed. The pretreated oil after removalof the solvent insoluble constituents is then heated or cooledto optimumtower countercur- ,go rent {treating temperatures. When employing phenolas the selective solvent in the treatment 'of petroleum oils boiling inthe lubricating oil range, I have found that it is particularlydestrable to approximately saturate the oil with phenol at a*temperature in the range below about 1 10 B. to 125 F. under conditionsto;pre cipitate'arela'tively'small percent of scilventinsolubleoilconstituents withoutthe formation'of two phasesconta'in ing an--appreciable amount of 'the selectivesolvent. *Feedoilisthen'filtered-to remove the insoluble constituents-and then heated tooptimum countercurrent treating temperatures generally in the range fromabout 150 F. to 225 F.

In order to 1 further illustrate the invention, the following example isgiven which should not be construed as limiting the invention-in-anymannor whatsoever:

. Example A lubricating oilhaving a "viscosity-of 135 Baybolt at210 -F.,a-gravity of 2434 A. 'P.-I.-derived drom Rodessa crude and'which hadbeen previpuslyacid treated and s'teamsweetened to remove the asphalticconstituents was solvent treated with phenol in various operations. Inthe first :operation the "feed oil was passed directly into a--eounterourrent treating tower. In asecond-opcreation the feed 'oil wasfiltered usingcentrifuges I and then 'passed irito :the counter-currenttreating tcrwer. In a l third operation a propane 'pre cipitatod oil:was passed directly into a countercurrent treating tower. "-In a fourthoperation conducted -in accordanee -with the process =dfthe presentinvention the "feedoil-wes saturated with phenol, filterediby'means ofpress filters 'and'then passed into the countercurrent treating "tower.

'l 'heresults of these operations wereas' follows:

00 Per cent phenol Maximum Percent cainsolu le..oil tower capacity;Dacity based meterialin all volumes of oil upon-operadeed iced per hourtioml Operation 1 0.124 400; -13. 3 Operation'.2 c '0. 13 620' 20. 7Operation 8, 0.03 2,30] '76. 6 QperahionA 0.01 3, 000 JLOO. 0

it is desired to claim all novelty in so far as the prior art permits.

I claim:

1; In a process for segregating into its relatively more aromatic andinto its relatively more parafiinic constituents a viscous petroleumlubricating oil substantially free of asphalts, which tends to developemulsification difliculties during solvent extraction, due to thepresence in said oil of a small amount, less than 2%, of dissolvedmaterial which precipitates out during solvent extraction in the form ofa finely divided insoluble solid which distributes itself between theinterfaces of the solvent and oil, the improvement comprising subjectingsaid oil to preliminary treatment at a temperature between about 110 F.and 150 F. with a solventhaving a preferential selectivity for therelatively more aromatic compounds as compared tothe relatively more,

tion with a large enough volume of the same selective solvent and undersuitable temperature conditions to cause the formation of two liquidphases.

2. In a process for the segregation into its relatively more aromaticand into its relatively more parafiinic constituents a viscous petroleumlubricating oil having a viscosity of about 135 seconds Saybolt at 210F. and a gravity of about 24.4" A. P. 1., derived from a Rodessa crudeoil, and which had been previously acid-treated to remove asphalticconstituents, which comprises mixing with said oil at a temperature ofabout to about F. a sufiicient amount of phenol, between about 5% andabout 20% to approximately saturate said oil therewith but insufiicientto cause the formation of two liquid phases, to precipitate a smallamount, less than 0.5% of the feed oil, of phenol-insoluble constituentsas a filterable solid phase, filtering said oil in a press filter toremove said solid precipitate and to produce a filtered oil free fromemulsifying tendencies when subjected to phenol extraction, and thencountercurrently extracting said filtered oil with phenol at atemperature of about F. to 225 F.

CHESTER L. READ.

